1. Field of the Invention
The invention concerns the examination of a body, by means of wave beams emerging therefrom. It applies more particularly, but not exclusively to tomography.
2. Related Art
The current embodiments in the field concern what may be termed "computed tomography" (see for example, the French Patent No. 74 14031 published under No. 2 227 582). The body to be examined is traversed by wave beams. Sensors in a specified position each receive a wave beam which emerges from the body with a specified direction. For each sensor, the sensed signals ("gross data") represent the accumulated effect of the body under radiation all along the trajectory of the wave beam in question.
In other words, each gross data signal represents the intensity of a wave beam of a given type which emerges from the body along an axis termed the "acquisition line". The axis in question may be designated by at least two parameters (such as a position parameter and an angular parameter). According to these axis parameters, the gross data define a "image of projections" of the radiation in a multidimensional space termed "space of projections". This is a dual space of real space (the physical observation space), because to each point of the space of projections, there corresponds a straight line and one only of real space.
Computed tomography is based on the following principle: if a sufficiently large set of gross data signals is available relating to acquisition lines passing through the body along different directions, then it must be possible to find the variation of absorption (or of emission) of the wave beam at each point of the examined body.
The drawback of computed tomography is that it requires a considerable number of calculations. It is therefore difficult and expensive to reconstitute the real image of the body in real time.